Performance of Canna indica floating treatment wetlands in the removal of Cr species.

DI LUCA, G. A.; MUFARREGE, M. M.; HADAD H. R.; MAINE, M. A.; NOCETTI, E.; CAMPAGNOLI, M.A

Simposio; 10th International Symposium on Wetland Pollutant Dynamics and Control, WETPOL.; 2023

Chromium contamination of water is caused by a variety of anthropogenic activities. Cr could enteraquatic ecosystems mainly in two oxidation states: Cr(III) and Cr(VI), exhibiting distinct chemical and physical properties, as well as different influences on living organisms. Floating Treatment Wetlands (FTWs) are a promising and cost-effective ecological engineering tool for the restoration of water bodies polluted with metals, among other contaminants. In this study, the efficiency of FTWs populated with Canna indica in the removal of Cr(III) and Cr(VI) was assessed. Also, metal distribution in the water-plant-sediment system was evaluated. The experiment was carried out in plastic reactors (70L capacity, containing 4 Kg of sediment and 38 L of water) placed outdoors under a semi-transparent plastic roof. FTWs were constructed so that only the roots and rhizomes were in contact with the water column. Four C. indica plants were placed in each FTW. The treatments were 5 and 10 ppm Cr(III) and 5 and 10 ppm Cr(VI), in both cases with Presence/absence of FTW. A Biological Control was included (with FTW, without Cr addition). All treatments were arranged in triplicate. The results showed an efficient removal of both Cr species in treatments with presence of FTWs, with removals greater than 80% after 35 days. Also, Cr removal was faster in treatments with FTW than in treatments without FTW.At the end of the experiment, Cr concentration increased in the sediment of all treatments. In Cr(III)treatments, the sediment from the reactors without FTW accumulated significantly more metal than the sediments with FTW, while the opposite occurred in the Cr(VI) treatments.Regardless of the presence or absence of FTW or the Cr species added, chromium accumulated in the sediment mainly bound to organic matter. However, in the sediment of the treatments without FTW, there was a significantly higher accumulation of Cr in the Fe-Mn oxides fraction compared to the treatments with FTW. C. indica accumulated Cr in their tissues regardless of whether it was added as Cr(III) or Cr(VI). In all treatments, the highest Cr concentration was determined in the roots of C. indica, while the lowest concentration was measured in leaves.FTWs populated with C. indica were efficient in the remediation of Cr-contaminated water, adding an aesthetic value to the treatment as it is an ornamental plant.